An adapter, also called as a power adapter, is configured to charge a device to be charged (such as a terminal). Nowadays, the adapter on the market typically charges the device to be charged (such as the terminal) in a constant voltage mode. When a current absorbed by the device to be charged (such as the terminal) is larger than a maximum output current that the adapter can provide, it may cause the adapter to enter an overload protection state, and thus the adapter cannot continue charging the device to be charged (such as the terminal).